Lasers are increasing being shown to be useful in a multitude of hard and soft tissue dental procedures, including: removing decay; cutting, drilling or shaping hard tissue; and removing or cutting soft tissue. A tooth has three layers: the outermost layer is the enamel which is the hardest and generally forms a protective layer for the rest of the tooth, the middle and bulk of the tooth includes dentin, and the innermost layer includes pulp. The enamel and dentin are similar in composition and include roughly 85% mineral, generally carbonated hydroxyapatite, while the pulp contains vessels and nerves. Laser radiations at wavelengths in the 9.3-9.6 micrometer range are well absorbed by the hydroxyapatite that forms a significant portion of tooth and bone, making such lasers efficient in the removal of hard tissue.
Lasers have also been found to be useful in the removal of dental material without needing local anesthetic that is typically required when a similar procedure is performed using a drill. Further, lasers do not make the noises and vibrations that are associated with dental drills. At least for these reasons, it is the hope of many in the dental industry that lasers may replace the drill and may eliminate or at least lessen the anxiety and fear from dental treatment.
A dental treatment laser having a wavelength in the 9.3-9.6 micrometer range is not visible to the human eye. Therefore, in addition to the treatment laser beam, a dental laser system may employ a marking/aiming laser beam in the visible spectrum. Such lasers may have a wavelength of about 532 nanometers (which is a green laser) or 650 nanometers (which is a red laser). If the marking laser beam and the treatment laser beam are collinear along a beam path, it is likely that the treatment laser beam will act upon substantially the same area where the marking laser beam impinges.
In many dental laser systems, the laser is housed in a console and is transmitted to a handpiece/main chamber assembly through an articulated or flexible arm, using optical devices such as mirrors, lenses, and/or fiber optic cables. The arm generally attaches to a main chamber to which a handpiece attaches, as well. The handpiece can be made detachable, e.g., for cleaning, servicing, etc. Differently configured handpieces, that are detachable, may be used for different dental procedures. At the end of the arm or within the main chamber, a beam guidance system may be located, that can be used to guide the laser beam towards a selected treatment area. The handpiece beam exit from which the laser beam exits is typically small for improved ergonomics and easier manipulation, e.g., within a person's mouth during laser-based dental treatment. It is usually desirable that the laser beam pass through approximately the center of the beam exit, so that an operator can target the handpiece toward a center of the area to be treated. The beam guidance system can then automatically move the laser beam according to certain shape, size, and scan parameters, such that at least a portion of the area to be treated around the targeted center is irradiated for fast, efficient, and effective treatment.
The beam guidance system may control the movement of the treatment laser beam to treat a portion of the tissue to be treated, where the portion has a particular preset shape. Alternatively, or in addition, an operator may specify a perimeter of the treatment area. A computer (any processor or processing unit, at least a part of which includes software) containing coordinates for a series of preset shapes and/or the user-specified perimeter may control the movement of the beam guidance system. To this end, a beam guidance system generally includes a pair of computer-controlled galvanometers. U.S. Patent Application Publication No. 2013/0059264 describes such a beam guidance system, and is incorporated herein by reference in its entirety.
There are numerous potential sources of position alignment error in the guidance of laser beams, particularly in a dental laser system. Often the alignment of the laser beam undergoes variations over time. These variations can result from: system vibrations, the system getting bumped, misalignment of different interchangeable handpieces, misalignment of the articulated arm, optical misalignment, geometric stacking errors, mechanical and/or electrical drift, and/or thermal deformations. The effects of beam alignment variation may combine over time and can result in a significant alignment degradation, that can prevent a proper, effective, and/or efficient use of the laser-based treatment system. Variability of laser beam alignment may adversely affect reliability of many laser-based treatment devices and especially of those devices that are equipped with articulated arm type beam delivery systems. Alignment of the laser beam in laser-based treatment devices is often a time consuming process that requires trained personnel and needs to be repeated on a regular basis.